Blowing headlight fuse

[Anonymous]

Hi all,
I've got an '82 GS750TZ (same as GSX750EZ but US speck.) I put in a new battery a couple of weeks ago and all was well. I noticed the other day that the headlight was looking very dull, checked the fuse which was blown and replaced. This then happened a couple of hundred times;

When I switch the ignition on the lights come on fine, as soon as I start the engine the headlamp fuse blows.

The lights are then okayish at tickover, get very dull at low revs, and back up to okayish at higher revs.

No other fuses have blown and the bike runs fine (was out yesterday for 120 miles with no problems.)

Have checked all wires and I can't see any signs of a short occuring.

Have checked grounding points and all seem fine.

If I disconect the reg/rec and try again the fuse dose'nt blow and the lights are fine.

I don't want to jump to the conclusion that it's the reg/rec when it could be something simpler (or cheaper), and I'm not totally sure that disconecting it proves anything. Can anyone offer any help before the world runs out of 10A fuses? Thanks.

[earlfor]

Re: Blowing headlight fuse

I sounds like youre blowing fuses because of too high a charging current/voltage. When the lighting fuse on the fuseblock blows, the 3rd stator phase if still powering the headlight and consequently, headlight brightness increases/decreases with rpm. I would check voltage at the battery terminals with the engine running at 5000 rpm. Voltage should be between 14.5 and 14.8. The upper limit is 14.9 volts and it must not exceed that level no matter how much rpm is ireaeased beyond 5k.

Earl

Hi all,
I've got an '82 GS750TZ (same as GSX750EZ but US speck.) I put in a new battery a couple of weeks ago and all was well. I noticed the other day that the headlight was looking very dull, checked the fuse which was blown and replaced. This then happened a couple of hundred times;

When I switch the ignition on the lights come on fine, as soon as I start the engine the headlamp fuse blows.

The lights are then okayish at tickover, get very dull at low revs, and back up to okayish at higher revs.

No other fuses have blown and the bike runs fine (was out yesterday for 120 miles with no problems.)

Have checked all wires and I can't see any signs of a short occuring.

Have checked grounding points and all seem fine.

If I disconect the reg/rec and try again the fuse dose'nt blow and the lights are fine.

I don't want to jump to the conclusion that it's the reg/rec when it could be something simpler (or cheaper), and I'm not totally sure that disconecting it proves anything. Can anyone offer any help before the world runs out of 10A fuses? Thanks.

[Anonymous]

Thats great, thanks. If that is the problem I assume the cause is the reg/rec?

[earlfor]

Yes, if voltage exceeds and holds a level higher than 14.8 or at most 14.9, then your R/R is faulty.

Earl

Thats great, thanks. If that is the problem I assume the cause is the reg/rec?

[leslo]

I had something sort of similar happen like that a few months ago - I knew my reg/rec was ok cause I replaced that beforehand, but I kept blowing headlight fuses and even the headlight itself a couple of times.
Turns out my headlight terminal connector (though it looked ok at a glance) was faulty. There was a bad connection in there somewhere that I couldn't see. Got a new one at Autozone for $2 and it all works fine now. I like cheap fixes.
Les

[earlfor]

Yep, I've had that happens also. With electrical problems, iall you can do is start with the most likely and work your way down the list. :-) Its always the last thing you check. :-)

Earl

Turns out my headlight terminal connector (though it looked ok at a glance) was faulty. There was a bad connection in there somewhere that I couldn't see. Got a new one at Autozone for $2 and it all works fine now. I like cheap fixes.
Les

[KGB]

I toasted mince due to the 90/100 watt H$ I was using 8O


I could always see where I was going, and people got out of the way

[Anonymous]

Hi all,
Thanks for all the help so far, it's been great. Sadly, the saga continues;

Checked the voltage across the battery (correct?) with the engine running/revving and got a reading of up to 17 volts (ouch).

Checked the massive box of spares I got with the bike and found a reg/rec, obviously no idea of its condition.

Excitedly fitted reg/rec and started her up.... blown headlight fuse. Damn.

The headlight definately got brighter with more revs before the fuse blew. so I'm assuming it's the same problem (dont have multimeter to hand to check it).

What's the likleyhood that the 2nd reg/rec had the same problem before I fitted it? Is there a possible fault/short that could damage the reg/rec when the bike is fired up? With a new fuse in and the reg/rec disconnected everything starts and runs fine, all pretty lights and no blown fuses.

I know their quite open ended questions but I dont want to spend out on a new reg/rec only to have it killed as soon as I fire the bike up.

Thanks in advance.

P.S. Just had a thought. Is it possible (however obscure) that there is a short from the stator and its bypassing the reg/rec completely. I know there a whole AC/DC thing involved buts it's the only thing I can think of. Please excuse me if thats a very stupid suggestion.

[earlfor]

I think the liklihood of the 2nd R/R being toasted is about 100%. No one buys a new one if the old one is working fine. :-) 17 volts is a dead giveaway. Its a goner and should only be used as a paperweight. My R/R
if I rev up the engine, will "spike" momentarily at about 14.9 -15 volts for a split second. Then it returns to 14.7 volts steady regardless of rpm. Your R/R is history.

Earl


[quote="daveb"]Hi all,

Checked the voltage across the battery (correct?) with the engine running/revving and got a reading of up to 17 volts (ouch).

Checked the massive box of spares I got with the bike and found a reg/rec, obviously no idea of its condition.

Excitedly fitted reg/rec and started her up.... blown headlight fuse. Damn.

The headlight definately got brighter with more revs before the fuse blew. so I'm assuming it's the same problem (dont have multimeter to hand to check it).

What's the likleyhood that the 2nd reg/rec had the same problem before I fitted it?

[argonsagas]

[quote="earlfor"]I think the liklihood of the 2nd R/R being toasted is about 100%. No one buys a new one if the old one is working fine. :-) 17 volts is a dead giveaway. Its a goner and should only be used as a paperweight. My R/R
if I rev up the engine, will "spike" momentarily at about 14.9 -15 volts for a split second. Then it returns to 14.7 volts steady regardless of rpm. Your R/R is history.

Earl


/quote]

Agreed, except for one small thing. As long as it hangs around and looks as though it is functional there is a chance you will try it again, or it will get passed on to someone else.

Don't do that. The R/R is useless. Get rid of it.

[Anonymous]

Hi All,
Sorted. Whilst waiting for the new R/R I took some time to go over both the bike and this forum. Found lots, fixed lots, learnt lots. Thanx to all concerned for all the help past, present and future. Much appreciated.
Dave B.